If you need to find your gas history, you can access it on Etherscan.io; there are two ways of accessing the information.
- Navigate to your wallet address, and locate the "TxnFees" section under the "Analytics" tab on your address' page:
- Click on the 'Transactions' tab on your address' page, instead of 'Analytics'.
- Scroll down, and you will see an button in the lower right labelled "Download CSV Export".
- This will allow you to download your transaction history in .CSV format (accessible as a spreadsheet), so you can manually calculate the fees.